SIMPSON, GEORGE GAYLORD

(b. Chicago, Illinois, 16 June 1902; d. Tucson, Arizona, 6 October 1984),

paleontology, vertebrate paleontology.

Simpson was an empirical paleontologist specializing in mammals; he led numerous expeditions to discover new fossils. These were described and analyzed in hundreds of technical publications. However, Simpson is best known for incorporation of evidence from fossils and earth history in understanding biological systematics and evolution. Simpson was a principal architect of the “modern synthesis” of evolutionary thought emerging in the 1940s.

Early Life and Education Simpson’s father, Joseph Alexander Simpson, was a successful attorney, first in Chicago and then in the frontier mining and railway city of Denver, Colorado. There he took advantage of opportunities for land development and then mining. Simpson’s mother, Helen Kinney, lost her own mother at a young age and was raised in Hawaii by grandparents who were Presbyterian missionaries there. George Gaylord Simpson was the third of three children. He had two sisters, Margaret and Martha, who were seven and four years older, respectively. The family was Presbyterian, but Simpson himself was never particularly religious.

Simpson grew up in Denver, in a Rocky Mountain environment where he enjoyed nature with family and friends. He credited camping, mountain climbing, and mining with his father for inspiring an interest in geology. These experiences made him comfortable outdoors, where he was to spend many months of his adult life. Looking back as an adult, Simpson felt that certain of his boyhood characteristics—his intelligence, shortness of stature, red hair, and visual impairment that limited ball playing— combined to foster antagonism from his peers. Serious and studious, Simpson advanced rapidly through school in spite of occasional setbacks due to health. He entered the University of Colorado at Boulder when he was age sixteen.

At the University of Colorado, Simpson was influenced by Arthur J. Tieje, who introduced him to the excitement and mystery of historical geology and paleontology, subjects that would inspire a lifetime of intensely focused scholarship. When Tieje left Colorado, he advised Simpson to transfer to Yale University as the best place to study paleontology. Simpson transferred in 1922, finished his AB degree in 1923 at Yale, and entered graduate school there to pursue a career in paleontology.

Soon after moving east, Simpson secretly married Lydia Petroja while he was still an undergraduate. Four daughters, Helen, Patricia (Gay), Joan, and Elizabeth, were born in the next six years, but the marriage ended in separation and divorce. In 1938 Simpson married again, this time to psychologist Anne Roe, a childhood friend from Denver. Simpson and Roe remained married until Simpson’s death forty-six years later.

At Yale, Simpson found a large and little-studied collection of North American Mesozoic mammals that he analyzed for his PhD. The Mesozoic Era in Earth history is popularly known as the age of dinosaurs, but it is also the time when mammals began their early diversification. Humanity’s history as mammals is deeply rooted in the Mesozoic, and it was natural that Simpson would seek to learn all he could of Mesozoic mammals. The dissertation was completed and the degree awarded in 1926. Simpson immediately moved to the British Museum of Natural History in London as a postdoctoral scholar to undertake a similar study of European Mesozoic mammals. The two resulting monographs— A Catalogue of the Mesozoic Mammalia in the Geological Department of the British Museum(1928) and “American Mesozoic Mammalia” (1929) established Simpson as a precocious but surprisingly mature authority on early mammal diversification and evolution.

Museum Work Returning from Europe in 1927, Simpson joined the American Museum of Natural History in New York as an assistant curator. He continued research on early mammals but moved up stratigraphically and forward in time to study the beginning of the major Cenozoic diversification of mammals. He worked first on North American faunas and in 1932 was invited to study a major collection of Paleocene mammals at the National Museum of Natural History in Washington, D.C. This required fieldwork in the Crazy Mountains Basin of central Montana to collect more specimens and determine their stratigraphic context. Samples for some species were large, requiring statistical characterization for diagnosis and comparison as once-living populations. The Crazy Mountains study, more than any of his previous works, enabled Simpson to quantify and compare evolutionary change through time, and it required implementation of a rational taxonomic framework capable of encompassing history. Simpson emphasized quantification and stratigraphy in a way that soon led to introduction of chronoclines as a way of quantifying how morphology changes through time (analogous to the spatial clines that quantify how morphology changes geographically).

Simpson’s curiosity about extinct mammals went beyond those known from North America, and in the 1930s he initiated two major paleontological field expeditions to Patagonia, the first in 1930–1931 and the second in 1933–1934. The purpose was to characterize the history of South American mammals evolving in isolation from the rest of the world. His popular journal of these expeditions, Attending Marvels (1934), has been read by many and reprinted several times. Research in Patagonia led to many publications summarized in a major systematic review, Beginning of the Age of Mammals in South America (1948), published in two parts over the course of two decades (part 2 appeared in 1967). Fieldwork in Patagonia initiated a lifelong interest in penguins, with a parallel series of publications on penguin fossils and evolution.

At the American Museum, Simpson worked tirelessly, publishing hundreds of technical reports and monographs documenting the morphologies and stratigraphic occurrences of North and South American mammals. But a decade into his career, he started to publish more synthetic works as well. Simpson collaborated with his wife, Anne Roe, on a classic 1939 book, Quantitative Zoology, that introduced statistical methods and population thinking to evolutionary disciplines that make little sense without them. It was eventually expanded and republished in 1960, with Richard Lewontin added as third author.

Modern Synthesis The late 1930s and early 1940s were pivotal for evolutionary thought as a broader understanding of genetics, biogeography, morphology, and paleontology coalesced into a “modern synthesis” in which gradual, step-by-step morphological evolution is understood to reflect the additive effects of small mutations, while larger-scale speciation and macroevolution are explained in the broader context of geography and environmental change. The conclusion was that small-scale mutation and selection are sufficient to explain what is seen today and in the evolutionary past, and macromutations are not required. The principal architects of the modern synthesis were Theodosius Dobzhansky (Genetics and the Origin of Species [1937]), Julian Huxley (Evolution: The Modern Synthesis [1942]), Ernst Mayr (Systematics and the Origin of Species [1942]), Simpson (Tempo and Mode of Evolution[1944]), and Bernard Rensch (Neuere Probleme der Abstammungslehre: Die Transspezifische Evolution [1947; New problems of phylogenetic systematics: Transspecfic evolution.]).

Simpson’s contribution to the modern synthesis was powerful because it combined his empirical paleontological, quantitative, and systematic experience and brought time on a macroevolutionary and geological scale to the subject. Tempo and Mode of Evolution is widely regarded not only as paleontology’s principal contribution to the modern synthesis, but as a capstone for the synthesis as a whole that integrated all of the relevant disciplines. Simpson developed methods to analyze rates of evolution through time and showed that these were variable. Another innovation was the introduction of the term quantum evolution in an attempt to explain the sudden appearance of new lineages and higher taxonomic groups that were otherwise unexplained. In the preface to a 1984 reissue of Tempo and Mode, Simpson noted that the “punctuation,” or sudden appearance of new species, that is part of current “punctuated equilibrium” theory is essentially a restatement of “quantum evolution” first proposed in Tempo and Mode: “origin of a species or other taxon by exceptionally rapid evolution.”

War Years and After Simpson served a two-year tour of duty in the U.S. Army during World War II from 1942 to 1944. He was a captain and major in the Mediterranean theater in Algeria, Tunisia, and Italy. Simpson was not greatly interested by war and even less enamored of authority. At one point he was attached to General George Patton’s headquarters in Sicily. Simpson wore a short, “pink” beard that displeased Patton, who sent an aide to tell Simpson to remove it. Simpson replied that his commanding officer was General Dwight Eisenhower, who had given him permission to have a beard, and that if Patton wanted it removed, he should take the matter up with Eisenhower (who was also Patton’s commanding officer). Simpson kept the beard.

Following the war Simpson published “Principles of Classification and a Classification of Mammals” (1945). It has served as a standard reference for more than fifty years, and it is still his most-cited work. Simpson’s experience with phylogeny and classification led eventually to his book Principles of Animal Taxonomy(1961). After the war Simpson was appointed chairman of the American Museum’s Department of Geology and Paleontology; simultaneously, he accepted a professorship of vertebrate paleontology at Columbia University.

Simpson was the first president of the Society for the Study of Evolution, founded in 1946, and he helped Glenn L. Jepsen and Mayr organize a pivotal 1947 symposium, Genetics, Paleontology, and Evolution at Princeton, New Jersey. He also set to work at this time revising Tempo and Mode, which was reissued in 1953 as an expanded Major Features of Evolution. Both of these books, classics as they are, remain widely cited.

In 1953 Simpson took his writing in a different direction when he signed a contract to develop a major new university-level biology textbook. This was titled Life: An Introduction to Biology, which appeared in 1957. This first edition was written with Colin S. Pittendrigh and Lewis H. Tiffney, and a revised edition of 1965 was written with William S. Beck. The book reflected the original authors’ strong conviction that there is a unified science of life—a science of biology—which is larger than the then often-separate disciplines of botany and zoology. It is a measure of the authors’ foresight, and to some extent the influence of the new text itself, that botany and zoology departments were subsequently merged in many universities across the United States.

Amazon Expedition Simpson was not always lucky. In 1956 he participated in a joint Brazilian-American Museum expedition to the Rio Alto Juruá at the headwaters of the Amazon. There, while clearing a campsite on 24 August, a tree fell on the fifty-four-year-old Simpson, giving him a concussion, dislocating a shoulder, and shattering a lower leg. It was a week before Simpson could receive adequate medical care, and he was unable to return to work full time at the American Museum of Natural History until 1958. The stress and strain of this long absence led to a series of administrative confrontations, and in 1959 Simpson resigned from the American Museum to accept an Agassiz professorship at Harvard University. Simpson retained his Agassiz professorship at Harvard through 1969, but he suffered a heart attack in 1964 and moved to Tucson and the University of Arizona in 1967 for the sake of his and Roe’s health. Simpson wrote many scientific articles, an autobiography titled Concession to the Improbable (1978), and numerous popular books during his remaining years in Arizona. One of these, Fossils and the History of Life (1983), is a semipopular extension of Major Features of Evolution.

Simpson died in 1984 of pneumonia and complications following a South Pacific cruise. His body was cremated and his ashes scattered in the Arizona desert. A short, introspective novel by Simpson, The Dechronization of Sam Magruder, was discovered and published posthumously. It is interesting for the insight it gives of an exceptional scientist struggling to understand and explain himself.

In retrospect, Simpson is seen as a disciplined and intensely focused scholar, known both for his commitment to observation and for his ability to organize ideas and synthesize interpretations. He was a prolific writer, but a gifted writer, too, able to convey ideas simply and clearly to a wide audience throughout his career. Simpson has been called the greatest paleontologist since Georges Cuvier and the most influential natural historian of the twentieth century. He received many honors, including election to the National Academy of Sciences of the United States in 1941, at the age of thirty-nine. Simpson was awarded the National Medal of Science in 1966 by President Lyndon B. Johnson.

BIBLIOGRAPHY

An extensive Simpson bibliography is included in Max K. Hecht, Bobb Schaeffer, Bryan Patterson, et al., “George Gaylord Simpson: His Life and His Works to the Present,” in Evolutionary Biology, vol. 6, edited by Theodosius Dobzhansky, Max K. Hecht, and William C. Steere. New York: Appleton-Century-Crofts, 1972. Simpson’s personal papers and correspondence are archived in the Library of the American Philosophical Society, Philadelphia, available fromhttp://www.amphilsoc.org/library/mole/s/simpson.htm.

WORKS BY SIMPSON

A Catalogue of the Mesozoic Mammalia in the Geological Department of the British Museum. London: British Museum (Natural History), 1928.

“American Mesozoic Mammalia.” Memoirs of the Peabody Museum of Natural History, Yale University, New Haven 3 (1929): 1–235.

Attending Marvels: A Patagonian Journal. New York: Macmillan, 1934.

Tempo and Mode in Evolution. New York: Columbia University Press, 1944.

Beginning of the Age of Mammals. New York: American Museum of Natural History, 1948.

With Glenn L. Jepsen and Ernst Mayr, eds. Genetics, Paleontology, and Evolution. Princeton, NJ: Princeton University Press, 1949. The proceedings of the International Symposium on Genetics, Paleontology, and Evolution held in Princeton, New Jersey, in 1947.

The Major Features of Evolution. New York: Columbia University Press, 1953. An expanded version of Simpson’s Tempo and Mode of Evolution.

With Colin S. Pittendrigh and Lewis H. Tiffney. Life: An Introduction to Biology. New York: Harcourt, Brace, 1957.

With Anne Roe and Richard C. Lewontin. Quantitative Zoology. Rev. ed. New York: Harcourt, Brace, 1960.

“The Beginning of the Age of Mammals in South America. Part 2, Systematics: Notoungulata, Concluded (Typotheria, Hegetotheria, Toxodonta, Notoungulata incertae sedis), Astrapotheria, Trigonostylopoidea, Pyrotheria, Xenungulata, Mammalia incertae sedis.” Bulletin of the American Museum of Natural History 137 (1967): 1–259.

Concession to the Improbable: An Unconventional Autobiography. New Haven, CT: Yale University Press, 1978.

Fossils and the History of Life. New York: Scientific American Library, 1983. A semipopular extension of Major Features of Evolution.

The Dechronization of Sam Magruder. New York: St. Martin’s Press, 1996. A posthumously published novel based on Simpson’s self-reflections.

OTHER SOURCES

Dobzhansky, Theodosius. Genetics and the Origin of Species. New York: Columbia University Press, 1937.

Gingerich, Philip D. “George Gaylord Simpson: Empirical Theoretician.” In Vertebrates, Phylogeny, and Philosophy, edited by Kathryn M. Flanagan and Jason A. Lillegraven. Laramie: Department of Geology and Geophysics, University of Wyoming, 1986.

Gould, Stephen J. “G. G. Simpson, Paleontology, and the Modern Synthesis.” In The Evolutionary Synthesis: Perspectives on the Unification of Biology, edited by William B. Provine and Ernst Mayr. Cambridge, MA: Harvard University Press, 1980.

Huxley, Julian. Evolution: The Modern Synthesis. London: G. Allen and Unwin, 1942.

LaPorte, Léo F., ed. Simple Curiosity: Letters from George Gaylord Simpson to His Family, 1921–1970. Berkeley: University of California Press, 1987.

———. George Gaylord Simpson: Paleontologist and Evolutionist. New York: Columbia University Press, 2000.

Mayr, Ernst. Systematics and the Origin of Species from the Viewpoint of a Zoologist. New York: Columbia University Press, 1942.

Rensch, Bernard. Neuere Probleme der Abstammungslehre: Die Transspezifische Evolution[New problems of phylogenetic systematics: Transspecfic evolution]. Stuttgart, Germany: Enke, 1947.

Philip D. Gingerich